Subcritical CO₂-expanded nanofibrous scaffold reinforced with alginate-collagen gel for controlled drug release in tissue regeneration

This study presents a porous, collagen-reinforced nanofibrous scaffold developed using subcritical CO₂-mediated expansion to address limitations in conventional 2D electrospun membranes. The 3D-expanded (EXP) architecture significantly increased porosity and fluid retention, enhancing inter-fiber spacing without compromising fiber morphology. Electrospun polyhydroxybutyrate-polyethylene glycol (PHB–PEG) nanofibers were loaded with Lawsone (L), an antioxidant phytochemical, and structurally reinforced with a collagen–alginate gel (COL). Scaffold expansion was achieved via subcritical CO₂ exposure under ambient pressure, followed by freeze-drying. The expanded scaffold (EXP-COL-L) exhibited enhanced mechanical strength (2.6 MPa), high crosslinking efficiency (82 %), and a sustained biphasic drug release reaching 66 % over 96 h. In vitro analysis using fibroblast cells confirms the biocompatibility of the matrix. The scaffold also offered cytoprotection under oxidative stress, maintaining 86 % viability after H₂O₂ exposure. ELISA-based cytokine profiling revealed downregulation of IL-6 and Connexin-43, and significant upregulation of IL-10, Collagen III, and Sphingosine kinase-1, highlighting anti-inflammatory and regenerative effects. This subcritical CO₂-fabricated scaffold offers a scalable, solvent-free route to engineer biomimetic, cell-responsive wound dressings. These findings demonstrate its potential as a next-generation tissue-mimetic platform for sustained drug delivery and enhanced wound healing